A double-layer injection molding casing is a kind of multi-component injection (Multi-Component Inject) molding casing, which has been widely used for casings of a variety of electronic apparatuses. Referring to FIG. 1, the double-layer injection molding casing includes an outer layer 1 and the inner layer 2 connected to each other. A component constituting the outer layer 1 and a component constituting the inner layer 2 are usually different (certainly, the outer layer 1 and the inner layer 2 each can be comprised of a variety of different components). Because the component of the outer layer 1 and the component of the inter layer 2 of the double-layer injection molding casing can be different, different portions of the casing can exhibit different properties so as to achieve multiple functions. For example, if the outer layer 1 and the inner layer 2 have different colors (e.g., bi-color injection molding casing), the casing can show different colors in appearance without being dyed. For another example, because an inner side of the casing of the electronic apparatus is used for being contacted with electrical components and an outer side of the casing of the electronic apparatus is used for being contacted with the external environment, it is necessary for the casing to have not only good insulativity and flame retardancy, but also good stain resistance and abrasion resistance. However, a material with such properties has a high cost. If the double-layer injection molding casing is used, so long as the inner layer 2 of the casing is made of a component with good insulativity and flame retardancy and the outer layer 1 of the casing is made of a component with good stain resistance and abrasion resistance, the casing can meet the performance demand of the casing of the electronic apparatus, thereby reducing the cost.
The double-layer injection molding casing is usually manufactured by using a multiple injection molding process (here for example, two injection molding process): at first, the outer layer 1 is formed by injection molding; before the outer layer 1 is entirely solidified, a half mould located at an inner side of the outer layer 1 is replaced (at the same time, the outer layer 1 is remained on a half mould located at an outer side thereof). Then, the inner layer 2 is formed by injection molding. During injection molding the inner layer 2, the outside layer 1 is actually used as a part of a mould cavity. After demoulding, the outer layer 1 and the inner layer are connected together automatically.
It is necessary to dispose a locating structure 3 comprised of a screw post 31 and a structure rib 32 on the inner side of the injection molding casing so as to locate components (e.g., circuit boards, electronic components, etc.) mounted in the injection molding casing, or to combine two parts of the casing together. In the prior art, the double-layer injection molding casing is manufactured by the multiple injection molding process. It is thought that, if the locating structure 3 is directly integrally formed with the inner layer 2 on the inner side of the inner layer 2 by injection molding, the issues such as the decrease of an appearance surface, the difficulty of demoulding the locating structure 3, and so on, will be caused. Thus, in the conventional double-layer injection molding casing, the locating structure 3 is manufactured separately (e.g., injection molding) as a separate part and then is adhered to the inner layer of the casing via a special glue or adhesive tape 33.
It is found by the inventors that the prior art at least has the following problems: since the locating structure of the conventional double-layer injection molding casing is separately manufactured, and the locating structure is adhered to the inner layer of the casing by using the special adhesive tape or glue, the manufacturing process of the conventional double-layer injection molding casing is complicated and has low production efficiency.